BAKU, Azerbaijan — Opposition parties in the former Soviet republic of Azerbaijan are calling for a boycott of the upcoming early presidential election.

The office of incumbent president Ilham Aliyev, who has ruled the oil-rich Caspian Sea nation since 2003, announced on Monday that the next presidential vote would be held in April, not in October as originally expected.

The only explanation that Aliyev’s office has provided for the unexpected decision was the fact that the country would be busy with various high-profile events during the fall.

The National Council of Democratic Forces, the country’s main opposition movement, said on Tuesday it would boycott the April 11 vote. In a statement, the movement’s chairman Jamil Hasanli called the early vote “an insult to elections.”